Septoria Leaf Spot Control: How to Identify and Get Rid of Septoria Leaf Spots

Septoria leaf spot or Septoria blight is often mistaken as early blight, but the two are actually different. It is a destructive disease that will start spreading infestation by affecting the aesthetics of the plant. In the worst situations, it can lead to 100% crop loss. Given its severity, it is important to know how to prevent Septoria leaf spot to minimize its damage, especially for commercial growers.

What is Septoria Leaf Spot?

Septoria lycopersici is the fungal pathogen that is primarily responsible for this disease. Although it can affect the host at any point, symptoms will initially appear on the stems nearer the fruit and on the older leaves. The fungus lives mostly on the fallen fruit of the host plant. It can also survive on the soil, weeds, and plant debris.

There are several ways by which Septoria leaf spot can transfer from one plant to another. Wind and water are two of the most common. They can splash on the plant from the soil in environments with extreme winds. It is also possible for the fungus to transfer to plants through contaminated equipment.

In terms of external conditions, on the other hand, the fungus will favor warm, wet, and humid environments. They prefer temperature that ranges from 60 to 80 degrees Fahrenheit. The fungus also likes leaves that are wet for a long time. With this, it is not surprising that they often attack plants after heavy rainfall.

Septoria Leaf Spot

Septoria Leaf Spot Symptoms on Fig Tree

Identifying Septoria Leaf Spot’s Damage

Host Plants

The pathogen that carries this plant disease infects only plants from the Solanaceae family, specifically tomato. Aside from tomatoes, they can also attack black nightshade, horsenettle, petunia, and potato, among others.


Unsure if your plants are already suffering from Septoria leaf spot? The following are some of the signs that you should watch out for:

  • Small and circular spots will appear on the older leaves. On average, they will have a diameter of 1/16 to 1/8 inch. They will have a distinct circular shape and can be numerous in one leaf. There are some points where they will meet and intersect, and hence, making the holes larger.
  • When there are holes in the leaves, it affects the photosynthetic activity of the plant. This results to the deprivation of essential nutrients. Hence, the leaves will show discoloration and dryness. They will eventually suffer from wilting.
  • Stems, calyxes, and blossoms will also show visible symptoms, not just the leaves. They will make some parts of the plant turn dry and brown. They will form lesions that are easily visible to the naked eye.
  • It is seldom that the disease affects the fruit. However, because of the defoliation, fruits like tomatoes can show spots of dryness as a result of too much heat from the sun since there are no leaves that could act as protective barriers from excessive heat.

Results of Infestation

Similar to the case of other common plant diseases, most of the infestations will lead to cosmetic damages. This will make the plant look unattractive. Different parts of the plant may discolor and dry. In severe cases, the plant will suffer from defoliation. It will not receive the nutrients that are necessary for its survival. In the case of tomatoes, the lack of leaves on the plant will make it prone to sun-scalding. If the problem is not addressed as soon as possible, this will be harder to treat. Hence, it is not uncommon for commercial growers to end up suffering from financial losses since their crops will no longer be marketable.

Septoria Leaf Spot

Most of the Infestations Will Lead to Cosmetic Damages

How to Get Rid of Septoria Leaf Spots

Natural and Organic Solutions

For an effective way to deal with Septoria leaf spot in the absence of worrying about toxicity, the following are some of the best things to do:

  • Prevention is better than cure, even in the case of Septoria leaf spot. With this, one of the best preventive measures is to choose the plants to grow. Make sure that the seeds are disease-free and that the seedlings are healthy. Grow plants that are resistant to the fungus that cause the problem.
  • Keeping the garden clean is another simple solution that can deliver great outcomes. Sanitation will go a long way. With this, remove any tomato or plant debris from the previous harvest. The fungus can overwinter on the plant, which is why it is important to take them out of the garden and to never use it for a compost.
  • Crop rotation will also be an effective solution. Because the pathogens can overwinter on the plants and soil, it is important to rotate crops every one to three years. Before planting any crop, see to it that the soil is in its best condition.
  • Improving air circulation will also help in lessening the susceptibility of plants to Septoria leaf spot. You can use stakes to raise the plant, allowing air to pass through. This will improve humidity and air circulation. It will also make it less likely for the fungus to easily travel from one plant to another.
  • Mulching will also help, especially around the lower part of the plant. The mulch will act as the protective barrier to prevent the fungal spores from transferring to the soil.
  • Practice the right watering techniques. Drip irrigation is the best method. At all costs, avoid overhead irrigation. This will make it easier for the fungi to survive. Also, as much as possible, water early in the morning. It will keep the foliage dry and make it less attractive for the carriers of Septoria leaf spot.

Chemical Solutions 

It is inevitable that there are some who would resort to the use of chemicals for the treatment of Septoria leaf spot. A lot tend to stay away from this solution because of toxicity. Nonetheless, as long as you choose the right product and follow the directions on its proper application, it can deliver a high level of effectiveness.

Among others, one of the most common chemicals is chlorothalonil. It is an active ingredient in chemical fungicides. To be specific, some of the products that contain this ingredient include Daconil, Fungonil, Tuffcide, and Repulse.

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